The present invention relates to an arrangement for determining the starting instant of the leading edge of a received high-frequency pulse V of the form: EQU V=A.(t-t.sub.o).sin 2.pi. Ft (t&gt;t.sub.o)
where:
V is the instantaneous voltage PA1 A is the slope (which is unknown) of the leading edge PA1 t is the time PA1 F is the frequency. PA1 the pulse must be detected in accordance with a linear law so as to respect the linearity of the slope of the leading edge; PA1 and the frequency of the pulse before detection must be high.
Arrangements of this type can be used with particular advantage in the field of radio navigation, for which use reference is made to the article in the periodical ALTA FREQUENZIA, entitled: "A New Technique for the Precision DME of Microwave Landing System" by CHIARINE et al, published in volume LI No. 5, September-October 1982. In this article mention is made, in paragraph 4, of an arrangement of the type defined in the opening paragraph. To have this arrangement function correctly, the following requirements must be satisfied:
Actually, in the intended field of application, the duration of the linear portion of the leading edge does not exceed 300 ns, while the required precision is approximately 30 ns. In order to obtain this precision, the period of the high frequency must be less than 30 ns, that is to say it must have a frequency exceeding 30 MHz. This makes impossible the otherwise advantageous technique of effecting the second frequency change, and consequently passing from the first intermediate frequency (63 MHz) to the customary second frequency (10 MHz).